368 Mr. C. Tomlinson on the Motion of 



The bottles exposed in or near a window will always have one 

 side colder than the other, and this colder surface will determine 

 the deposit. Generally the side nearest the window is the cold- 

 est (seeing how little sun we have, and how long our nights are), 

 and here the deposit is most copious ; but when the sun shines 

 on the window, and the side nearest the light is the hottest, a 

 deposit is naturally made on the furthest side. This furthest 

 deposit, however, is but transient. It disappears when the sun 

 goes off the window, because the furthest side ceases to be the 

 coldest. It goes, in fact, to augment the increasing deposit on 

 the coldest side, or that nearest the light. I could always tell 

 whether there had been any morning sun, by inspecting the east- 

 staircase bottles on descending to breakfast. During the last 

 spring and summer there would sometimes be sunshine and 

 furthest deposits at 5 or 6 o' clock a.m., while clouds or rain would 

 come on about 8, and the furthest deposits would disappear during 

 the day. 



It is scarcely necessary to prove that a large bottle placed in 

 the window will be hottest on the side next the light when the 

 sun is shining on the window, and coldest at other times, except 

 perhaps during some of the warmest days of our short summer, 

 when the external temperature is equal to, or even higher than 

 the internal ; but as I am supporting a new theory against the 

 united testimony of many illustrious philosophers during three 

 quarters of a century, it is scarcely possible for me to overstate 

 my case. I will therefore give a few more details. 



A glass shade with its mouth upwards was placed on a small 

 table about 2 feet from a west window. Two thermometers 

 which marked the same temperature were hung within it, one 

 at the front or nearest the light, and the other at the back or 

 furthest from it. The open mouth was then covered with a flat 

 book. This was on the afternoon of the 7th of July, the weather 

 being cloudy, with occasional bursts of sun. In half an hour 

 the front thermometer read 82°, the back 78°. In another thirty 

 minutes the weather was cloudy, windy, and threatening for rain; 

 front 76°, back 74°. In another thirty minutes, during which 

 heavy rain fell, the temperatures became inverted ; the front was 

 now 68°, and the back 74°. The colder temperature was on the 

 side nearest the window during the night, and not until the 

 sun had come round next day did the nearer side become the 

 warmer. 



Now if fresh bottles of camphor be placed near the window at 

 intervals during all these mutations of temperature, it will be 

 found that the deposits go to or from the light according as the 

 front or the back of the bottle is the colder. There is no evidence 

 of this fact more satisfactory than actual measurement ; and to 



